1. Field of the Invention
The present invention relates to a material for a positive electrode, an electrode sheet for an all-solid state secondary battery, an all-solid state secondary battery, and methods for manufacturing an electrode sheet for an all-solid state secondary battery and an all-solid state secondary battery.
2. Description of the Related Art
For lithium ion batteries, electrolytic solutions have been used. Attempts are underway to produce all-solid state secondary batteries in which all constituent materials are solid by replacing electrolytic solutions with solid electrolytes. Reliability in terms of all performance of batteries is an advantage of techniques of using inorganic solid electrolytes. For example, to electrolytic solutions being used for lithium ion secondary batteries, flammable materials such as carbonate-based solvents are applied as media. In secondary batteries in which the above-described electrolytic solutions are used, a variety of safety measures are employed. However, there may be a concern that disadvantages may be caused during overcharging and the like, and there is a demand for additional efforts. All-solid state secondary batteries in which non-flammable electrolytes can be used are considered as a fundamental solution therefor.
Another advantage of all-solid state secondary batteries is the suitability for increasing energy density by means of the stacking of electrodes. Specifically, it is possible to produce batteries having a structure in which electrodes and electrolytes are directly arranged in series. At this time, metal packages sealing battery cells and copper wires or bus-bars connecting battery cells may not be provided, and thus the energy density of batteries can be significantly increased. In addition, favorable compatibility with material for a positive electrode capable of increasing potentials and the like can also be considered as advantages.
Due to the respective advantages described above, all-solid state secondary batteries are being developed as next-generation lithium ion batteries (New Energy and Industrial Technology Development Organization (NEDO), Fuel Cell and Hydrogen Technologies Development Department, Electricity Storage Technology Development Section, “NEDO 2013 Roadmap for the Development of Next Generation Automotive Battery Technology” (August, 2013)). For example, JP2006-164783A describes a battery in which an electrode having an active material layer including an active material, a solid electrolyte, and solid electrolyte particles having a higher ion conductivity than the solid electrolyte and a collector laminated on the active material layer is used.